\begin{tikzpicture}
    \pgfmathsetmacro{\a}{2.5}
    \pgfmathsetmacro{\c}{3}

    \tkzDefPoints{0/0/c1, \c/0/c2, 0/0.8/a1, \a/0.8/a2}
    \tkzDrawSegments[xianduan={below=0pt}](c1,c2)
    \tkzLabelSegment[above](c1,c2){$c$}
    \tkzDrawSegments[xianduan={below=0pt}](a1,a2)
    \tkzLabelSegment[above](a1,a2){$a$}

    \begin{scope}[yshift=-3cm]
        % 1
        \tkzDefPoints{0/0/B, \a/0/C}
        \tkzDrawSegment(B,C)
        \tkzLabelPoints[left](B)
        \tkzLabelPoints[right](C)
        \tkzLabelSegment[below](B,C){$a$}

        % 2
        \tkzDefLine[perpendicular=through C,normed](B,C)  \tkzGetPoint{d}
        \tkzDefPointOnLine[pos=2.5](C,d)  \tkzGetPoint{D}
        \tkzDrawSegment(C,D)
        \tkzLabelPoints[right](D)

        % 3
        \tkzInterLC[R,near](D,C)(B,\c)  \tkzGetFirstPoint{A}
        \tkzCompass(B,A)
        \tkzLabelPoints[right](A)

        % 4
        \tkzDrawSegments(A,B)
        \tkzLabelSegment[above](B,A){$c$}
    \end{scope}
\end{tikzpicture}

